Vayne is a real threat yes but what champion isnt honestly. If you want to shut one down long enough to kill or get away what u need to do is cc the crap out of her cause the biggest threat really is her tumble. you stop her from doing that she cant catch you as easily and get off the shots for her true damage. STAY AWAY FROM WALLS as much as possible the stun is nasty in combo with her tumble before the condem shot. She requires alot of mobility due to her passive where she gains a speed boosts when shes running towards champions. All in all my honest opinion is she isnt that op ive seen other ad carries build tank and dps and play just as well as her. Her biggest down fall is the mobility. And alot of her stats like her dmg from lane phase to group fights heavily depend on ruins and quints.